JOHANNESBURG - Miner and commodities trader Glencore, which is reviewing its operations in the face of a slump in commodities prices, announced more job cuts at its mines in South Africa on Thursday.

Gugulethu Maqetuka, a spokesman for Glencore in South Africa, said the Swiss-based company had laid off 240 workers at its South Witbank coal mine in northeastern Mpumalanga province, which had been shut down after reaching the end of its life.

The company was also in talks with labour unions about closing its ageing Witcons coal-processing plant, in Mpumalanga, which will affect 100 employees, Maqetuka said.

Glencore, hit hard by plunging commodities prices and under pressure from investors to cut its debt pile of nearly $30 billion, has already announced that about 380 jobs would be axed at its Optimum Coal subsidiary in South Africa after the closure of some operations at the mine.

It is also considering closing its Eland platinum mine in South Africa due to falling prices, putting just under 1,000 jobs there at risk.

Maqetuka said the closure of the South Witbank mine would affect 378 employees in total, including 138 who were being relocated to other operations.

Other mining companies are also cutting jobs. South Africa's National Union of Mineworkers said on Monday that about 22,000 jobs are under threat in the country's beleaguered mining industry.

The mining ministry has held several rounds of talks with companies and unions over planned job cuts, as President Jacob Zuma's government frets over high unemployment ahead of key elections next year.